Rivastigmine is one of the acetylcholine esterase inhibitors and is used as a therapeutic agent for Alzheimer's dementia (anti-dementia drug).
For such an anti-dementia drug, oral administration such as a tablet, a capsule, syrup, and granules, and administration by injection or through the rectum have been studied depending on a medicinal agent or a disease condition. In recent years, transdermal administration, that is, administration using a transdermal patch has also been developed for such an anti-dementia drug.
It is considered that the rivastigmine is relatively easily oxidized, and it is indicated that decomposition products of the rivastigmine may increase with time. To address this, a technique of adding an anti-oxidizing agent into a transdermal patch containing the rivastigmine has been developed (for example, Patent Document 1 and Patent Document 2). Patent Document 2 discloses a preparation in which a storage layer containing the rivastigmine is laminated to a silicone pressure-sensitive adhesive. However, the silicone pressure-sensitive adhesive itself is expensive and a release liner for such a silicone pressure-sensitive adhesive needs special treatment. Hence, the preparation has a problem of high cost.
Each transdermal patch disclosed in Patent Document 1 and Patent Document 2 uses an acrylic pressure-sensitive adhesive containing a carboxy group. However, the use of such an acrylic pressure-sensitive adhesive is considered to affect the oxidation of the rivastigmine to not a little extent. To address this, there is a report that the use of a pressure-sensitive adhesive having no carboxy group and no hydroxy group as the acrylic pressure-sensitive adhesive enables the formation of a transdermal patch excellent in temporal stability of the rivastigmine (Patent Document 3).
In order to improve skin permeability of the rivastigmine or to reduce skin irritation caused by a pressure-sensitive adhesive layer, a transdermal patch using a hydroxy group-containing acrylate-rubber hybrid pressure-sensitive adhesive (Patent Document 4) and a transdermal patch including an acrylic pressure-sensitive adhesive layer that has a hydroxy group, etc. and that contains a nonvolatile substance such as citric acid in order to reduce the loss of an active substance (medicinal agent) due to vaporization in the production process (Patent Document 5) have been developed. However, there is no discussion on the stability of the rivastigmine in these documents.